I am the husband of a PGY2 surgical resident. Let me say that medical school is a cakewalk compared to the PGY residency years. Now before that freaks you out....the good news. During the 4 years of med school, you learn how to accept, deal, and help. Here is what I did and what I learned in the first 4 years of her career that saved my marriage...literally. I learned to be;
1) self sufficient-She needed her space...badly. No loud and distracting TV where she was studying. My option was either having her at school studying all night or at home. I chose to turn off the TV and read a book myself to maximize our time even if she was face down in a book most of the time. I also learned the joys of video games and medical text books..which leads into
2) get involved. If you really want to support a med student/ resident, take an interest in the stuff they study and do. I never gave medicine a second thought past a physical...then I thumbed through her Surgical Anatomy book during her 2nd year and WOW. I started to read articles in JAMA and JACS and when I didn't understand something I would ask her over dinner. She got a charge out of me taking an interest in her job and I loved chatting with her about stuff even if I didn't totally understand it. That also lead to her asking me to help her study, make note cards, quiz her etc....you can maximize you time together simply by taking an interest and that way she/ he can come to you when they need a quizzer or someone to help them organize instead of going to another med student.
3) pack a lunch-seriously. I was the world's worst cook aside from a frozen pizza but by the MSIII year, I was a regular Emeril. My wife always tells me that she would starve without me. I work full time so it wasn't easy but again...it is not just their investment, it is yours too despite what people say. I would (and still do) wake up before her, make her coffee and an English muffin; pack her lunch with a sandwich I made the night before; and that night I would toss some chicken in the oven, steaks on the grill, or a Lean Cuisine in the microwave and we would spend the next 30 mins to an hour catching up on our days.
4) now this is the big one....learn that they are not helpless children that you must wait hand and foot on.
When you start doing things to help, sometimes that can be taken advantage of and it can become expected times 20. When they moan and whine, support them first then, if it continues, remind them this was their choice and you are just along for the ride and that just because they have MSXX or MD after their name doesn't make them or their problems or feelings any better, worse, or more important then yours
I would say that all the time and while my wife knew I was being a jerk, it gave her a reality check that while she is reading, sleeping, cutting fat off a cadaver, taking tests, rotating, etc...I was taking care of the dogs, cooking, cleaning, and keeping our family at bay when they called to complain about her not speaking to them for weeks.
5) meet the others-if your spouse/ significant other gets into it and has time, go along with then when MSI-IV interview prospective students. My wife became the interview coordinator in her 3rd year and she would have to set up the meet and greets after the interviews were over and the shing-dig the night before. I went to every one. This gave me the chance to meet the other students she went to school with but it also was a chance to meet other spouses of current med students AND spouses that came on the interview trail. I also made it a point to go to every social function she attended. I met her professors, program directors, etc and that was really cool. It brought us closer because it became a mutual interest even though I wouldn't be an MD if you paid me (too stressful).
But finally and most importantly....listen to them when they talk (make them listen to you too!) and understand that, depending on what field they opt to go into, it might not get easier for a long time. You will fight, yell, and wonder why the hell you bother doing things when your MS or MD spouse dosen't seen to care. You might even, after 4 years, suddenly have to move far away from family, friends, familiarity to a strange city when they graduate and start residency (we did) and that might be a hell of a pill to swallow. But...if you love that person and you are in it for the long haul, it will be OK because they will be there and sometime that is all that matters.
I hope my experience is translatable to you. If not..maybe some of it will help. Either way...patience, love, friends, a hobby or two, and each other ..that's all you need!
Good Luck!